The present invention relates to a gasket of a fibrous and/or porous material, and more particularly to a cylinder head gasket which is made of a disc of soft material, which is partially or completely saturated with a liquid.
Cylinder head seals for internal-combustion engines often are made of a fibrous material, such as, for example, asbestos, which is possibly reinforced with one or a plurality of imbedded or superimposed metal plates. The starting material for such cylinder head gaskets is an asbestos fiber mass mixed with binders such as natural or synthetic rubber, and which is connected with the metal plates in the form of a disc.
Cylinder head gaskets contain passages for the combustion chamber, the coolant and the lubricant. In the region of these passages the sealing edges must be particularly tight against the hot gases of the combustion chamber which gases are under high pressure, against the lubricant and against the coolant which might contain anti-freeze. A simple gasket made of asbestos fiber, binder and possibly reinforcing metal plates is not sufficient for this purpose because the cross-sectional density of the porous asbestos fiber material is unsatisfactory and the media to be sealed can pass through the seal. An additional improvement in the density of the asbestos material is required.
In the past, the microseal at the surface of cylinder head gaskets has been improved by providing the gaskets with coating layers. Also the cross-sectional density of the asbestos fiber layer has been improved by impregnating or saturating the asbestos fiber layer with suitable impregnating or saturating agents. The impregnating or saturating agents that have been used include solutions, dispersions, emulsions or latexes of polymerized or polymerizable substances. According to German Pat. No.1,072,032, for example, the impregnation is effected with such agents, but only in the immediate region of the passages. According to still other methods, self-drying vegetable oils, such as linseed oil with or without additives (see, for example, German Pat. No. 740,388 and U.S. Pat. No. 2,040,348), are used as the impregnating agent.
In the above-mentioned methods there exists the drawback that the polymerized or polymerizable material is applied to the asbestos fiber layer together with a solvent, a dispersing agent or an emulsion agent. These components are volatile and evaporate in the subsequent drying process and this evaporation produces cavities or pores and causes the fibrous material to swell. Subsequently the fibrous material must be pressed to increase its density and become particularly capable of sealing.
The use of self-drying oils of a vegetable origin also has not found acceptance for impregnating purposes. Presumably, the reason is that the resinified oils, such as linseed oil, are saponifiable and not sufficiently resistant against lubricants, water and combustion gases.